This invention relates to a disc brake caliper assembly, and more specifically, the invention relates to a disc brake caliper assembly that prevents piston knock-back.
Disc brake caliper assemblies are widely used in the automotive industry for applying a braking force to the wheels of a vehicle. The wheels are secured to a brake rotor, which has brake pads arranged on either side of its braking surfaces. A piston supported in the caliper housing forces the pads together and into engagement with the rotor when the vehicle operator depresses the brake pedal. Ideally, the brake pads do not engage the rotor when the brakes are not applied, which is a condition known as zero drag, so that frictional losses that reduce fuel economy are prevented. Typically, a retraction seal is used between the caliper housing and the piston to automatically retract the piston when the brakes are not applied.
Under severe operating conditions, the rotor may deflect due to vibrations or harsh road inputs. A deflected rotor may push back on the brake pads and force the piston into the caliper housing. As a result, an undesirable clearance between the rotor and brake pad may be created which increases the distance the operator must depress the brake pedal. Passive anti-knock-back devices have been employed, such as resilient rings, to prevent the piston from being forced into the caliper housing. However, as with many passive devices, the prior anti-knock-back device lacks fine control and responsiveness.
Electric parking brake actuators have been used to replace the mechanical devices typically employed to apply the parking brake. The electric actuators lock the piston in place once the brake pads have been forced together about the rotor. However, these actuators have been underutilized in that they only have been used for the limited purpose of applying the parking brake. Therefore, what is needed is an active anti-knock-back device that also may be incorporated into the electric parking brake actuator.
The present invention provides a disc brake caliper assembly that includes a housing having a bore. A piston is arranged within the bore and is movable between normal retracted and knock-back positions. A linkage is adjacent to the piston and is movable between first and second positions with a clearance between the piston and the linkage in the first position. The clearance undesirably permits the piston to move to the knock-back position during severe operating conditions. An actuator, which also may be used as part an electric parking brake, moves the linkage from the first position to the second position to eliminate the clearance when the linkage is moved from the first position to the second position where the linkage abuts the piston. The linkage is connected to the caliper housing by a support. The linkage prevents the piston from moving from the normal retracted position to the knock-back position.
In operation, the present invention prevents piston knock-back by sending an adjustment signal from a controller to the actuator at a predetermined interval. The signal commands the actuator to move a linkage from the first to the second position where the linkage abuts the piston. In this manner, the linkage prevents the piston from moving from a normal retracted position to a knock-back position.
Accordingly, the above invention provides an active anti-knock-back device that also may be incorporated into the electric parking brake actuator